Nuclear transparencies for nucleons, knocked-out under various semi-inclusive conditions

Using hadron dynamics we calculate nuclear transparencies for protons, knocked-out in high-$Q^2$, semi-inclusive reactions. Predicted transparencies are, roughly half a standard deviation above the NE18 data. The latter contain the effects of binned proton missing momenta and mass, and of finite detector acceptances. In order to test sensitivity we compare computed transparencies without restrictions and the same with maximal cuts for missing momenta and the electron energy loss. We find hardly any variation, enabling a meaningful comparison with data and predictions based on hadron dynamics. Should discrepancies persist in high-statistics data, the above may with greater confidence be attributed to exotic components in the description of the outgoing proton.Comment: 13 pages + 3 figsin appended PS file, report # WIS-94/43/Oct-P

Minimización del tiempo total de flujo de tareas en una sola máquina: Estado del arte

La programación de operaciones en una sola máquina es un problema clásico de la investigación de operaciones. Numerosos métodos han sido propuestos para resolver diferentes instancias del problema, dependiendo de las restricciones impuestas y del objetivo del mismo. En este artículo estamos interesados en ilustrar el estado actual de desarrollo de los métodos y algoritmos existentes en la literatura para el problema de minimización del flujo total de tareas sujetas a fechas de llegadas, tanto en problemas estáticos como dinámicos. Además, las posibilidades de trabajo y las preguntas abiertas serán igualmente expuestas

Manufacturing flow line systems: a review of models and analytical results

The most important models and results of the manufacturing flow line literature are described. These include the major classes of models (asynchronous, synchronous, and continuous); the major features (blocking, processing times, failures and repairs); the major properties (conservation of flow, flow rate-idle time, reversibility, and others); and the relationships among different models. Exact and approximate methods for obtaining quantitative measures of performance are also reviewed. The exact methods are appropriate for small systems. The approximate methods, which are the only means available for large systems, are generally based on decomposition, and make use of the exact methods for small systems. Extensions are briefly discussed. Directions for future research are suggested.National Science Foundation (U.S.) (Grant DDM-8914277

Induction of oxidative stress as a mechanism of action of chemopreventive agents against cancer

Prevention is a promising option for the control of cancer. Cellular redox changes have emerged as a pivotal and proximal event in cancer. In this review, we provide a brief background on redox biochemistry, discuss the important distinction between redox signalling and oxidative stress, and outline the ‘multiple biological personalities' of reactive oxygen and nitrogen species: at low concentrations they protect the cell; at higher concentrations they can damage many biological molecules, such as DNA, proteins, and lipids; and, as we argue here, they may also prevent cancer by initiating the death of the transformed cell. Nitric oxide-donating aspirin is discussed as an instructive example: it generates a state of oxidative stress through which it affects several redox-sensitive signalling pathways, leading ultimately to the elimination of the neoplastic cell via apoptosis or necrosis. As additional examples, we discuss the chemopreventive n–3 polyunsaturated fatty acids and conventional nonsteroidal anti-inflammatory drugs, which induce cell death through redox changes. We conclude that modulation of redox biochemistry represents a fruitful approach to cancer prevention

Electrophile-induced ether transfer: Stereoselective synthesis of 2,6-disubstituted-3,4-dihydropyrans

(Chemical Equation Presented) Stereoselective synthesis of trans-2,6-disubstituted-3,4-dihydropyrans has been achieved from a simple homoallylic alkoxyether via a three-step sequence: electrophile-induced ether transfer, cyclization, and functionalization, which is highlighted by a rare example of Ferrier rearrangement of allylic ether. This methodology was successfully implemented for the asymmetric synthesis of a C7-C17 fragment of swinholide A. © 2008 American Chemical Society

Minimización del tiempo total de flujo de tareas en una sola máquina: Estado del arte

La programación de operaciones en una sola máquina es un problema clásico de la investigación de operaciones. Numerosos métodos han sido propuestos para resolver diferentes instancias del problema, dependiendo de las restricciones impuestas y del objetivo del mismo. En este artículo estamos interesados en ilustrar el estado actual de desarrollo de los métodos y algoritmos existentes en la literatura para el problema de minimización del flujo total de tareas sujetas a fechas de llegadas, tanto en problemas estáticos como dinámicos. Además, las posibilidades de trabajo y las preguntas abiertas serán igualmente expuestas

Electrophile-Induced Ether Transfer: Stereoselective Synthesis of 2,6-Disubstituted-3,4-Dihydropyrans

Stereoselective synthesis of trans-2,6-disubstituted-3,4-dihydropyrans has been achieved from a simple homoallylic alkoxyether via a three-step sequence: electrophile-induced ether transfer, cyclization, and functionalization, which is highlighted by a rare example of Ferrier rearrangement of allylic ether. This methodology was successfully implemented for the asymmetric synthesis of a C7−C17 fragment of swinholide A